~In a short time span Arctic spring and autumn days have shortened.
~A very good reason why Northern Hemisphere circulation is changing aside from warming temperatures: thinner sea ice.
~ This can be visually observed multiple ways, all to to with atmospheric refraction.
The latest Arctic warming can be summed up in 3 periods by sunset tardiness, of which some part of the sun disk can be seen well below the astronomical horizon (A.O. : horizon seen if there was no atmosphere). In the High Arctic Cornwallis Island some sun disks parts have been seen lower than -3 degrees (that is 3 degrees of arc below astronomical horizon). Furthermore when seen so much below the A.O. under the violet sky, sunsets shift Northwards quite a lot, prolonging the day. 3 recent periods of concern would certainly be 2001-2005 , the last thicker ice years, 2005-2010 intermediate warming/thinning of sea ice, 2011 to 2021 severe thinning years, of which the first period had 6 Month of March sunsets 2 degrees below astronomical horizon, the intermediate period had 3, the longest lasting period of 11 March months had only 3, this is a serious decline in optical properties caused by sea ice and air interface. Visually this can be studied in greater details, although I have no illusions about how convincing these images can be, atmospheric refraction is very poorly understood, I'll endeavor to explain nevertheless: